A method for the laboratory cultivation of gonococci has been developed in this laboratory which allows for subsequent quantitative in vitro phagocytosis studies of viable gonococci. Employing a modification of the Maaloe technique, studies have demonstrated that log phase virulent gonococci possess antiphagocytic surface factor(s). Phagocytosis of stationary phase virulent and log phase avirulent gonococci readily occurs with subsequent rapid intracellular killing, demonstrating that gonococci do not survive or multiply within human phagocytic cells. Recent morphologic studies also demonstrate that log phase virulent gonococci attach to the surface membrane of human phagocytic leukocytes. Further studies outlined in this proposal are: (1) to purify and characterize gonococcal antiphagocytic surface factor(s), (2) to detect and characterize type-specific gonococcal opsonins, (3) to characterize the non-immunologic and immunologic parameters associated with attachment of gonococci to phagocytic leukocytes and other mammalian cells, (4) to study similar parameters associated with ingestion of gonococci, and (5) so study the effect on phagocyte metabolism of attachment of gonococci to leukocyte surface membranes. These studies should make possible a greater understanding of the immunobiology of the gonococcus and the pathophysiologic mechanisms associated with gonococcal disease.